The invention concerns a regulated axial biasing unit. This biasing unit comprises a first ramp disk and a second ramp disk, a plurality of ramp contours being configured on said first and second ramp disks. The biasing unit further comprises an annular cage carrying a plurality of rolling elements and inserted between the first ramp disk and the second ramp disk. One of the two ramp disks comprises a toothed segment. Accordingly, the other of the two ramp disks comprises an anti-rotation device.
Biasing units of the aforesaid type are used in transmissions of automotive vehicles, particularly to enable the actuation of a friction clutch in the drive train of an automotive vehicle.
German patent specification DE 10 2005 053 555 B3 discloses am axial adjusting device in form of a ball-and-ramp arrangement. The axial adjusting device comprises two disks centered on a common axle, one of the disks being axially supported and the other disk being slidingly displaceable, at least one of these disks being rotatably operable. The two disks comprise on their mutually facing front end surfaces, a same number of ball grooves extending in peripheral direction. Both disks are therefore mounted through rolling elements in form of balls.
U.S. Pat. No. 5,485,904 likewise discloses a biasing unit whose ramp disks can be rotated relative to each other by means of rolling elements in form of balls.
Similarly, U.S. Pat. No. 5,620,072 also discloses a biasing unit for a multi-disk clutch whose ramp disks are likewise rotatable relative to each other through rolling elements in form of balls.
German patent specification DE 10 2004 015 271 B4 discloses a torque transmission device. In this case, the rolling elements and the thrust bearing are arranged on a pitch circle of the same diameter. Balls are used as rolling elements.
The unpublished German patent applications based on invention reports E 2007 676 and E 2008 015 describe the mode of functioning of an axial biasing unit. Here, a biasing unit comprises a cage for rolling elements which is configured with pockets corresponding in number to the rolling elements to be retained. Each of the rolling elements is in contact with a ramp contour in the first ramp disk and with a ramp contour in the second ramp disk. When at least one of the two ramp disks is turned relative to the other ramp disk, the rolling elements ascend and/or descend along the ramp contours. The pockets for the rolling elements are configured such that, irrespective of the position of the rolling elements relative to the ramp contour, the pockets do not make any contact with the respective ramp contour.
The biasing units described above are uncontrolled biasing units comprising balls or rollers. The axial force of such biasing units depends on the torque take-up and cannot be actively controlled. The uncontrolled biasing units are used, for example, in optional all-wheel drive systems. In contrast, in differential gears with torque vectoring and in certain power take-off gears, the torque between the wheels or between the front and the rear axle is purposefully and actively controlled. In this case, one of the ramp disks comprises an outer gearing which is actuated through one or more cylinder gear steps or a worm gear by an electro motor.
Analogously, for an optional all-wheel drive, the ramp disks including the gearing are manufactured as solid parts. Feasible manufacturing methods are sintering, casting or forging. The biasing clutch is made up of a plurality of separate parts which, in the final analysis makes assembly and handling more difficult.